Point-of-care ultrasound in the acute abdomen and gastrointestinal emergencies: An evidence-based guide and the case for standardisation

Table 1 Diagnostic performance, heterogeneity and risk of bias of emergency point-of-care ultrasound applications in the acute abdomen

Ref.	Population/setting	Operator	Reference standard	Diagnostic threshold	Sensitivity (95%CI)	Specificity (95%CI)	LR+/LR-	Studies/patients	Heterogeneity (%)	Risk of bias/certainty	Interpretation and limitations
SBO: Study-level meta-analysis (Gottlieb et al[9], 2018)	ED and inpatient adults with suspected SBO	Mixed (EP and others)	CT, surgery, or final diagnosis	Dilated loop > 25 mm	92.4% (89.0%-94.7%)	96.6% (88.4%-99.1%)	27.5/0.08	11/1178	NR in retrievable text	QUADAS-2 not reported in retrievable text; no GRADE	Strong rule-in; study-level pooling may overestimate sensitivity
SBO: IPD meta-analysis (Shokoohi et al[10], 2023)	Multicentre ED, adults	EP (attending and resident)	CT/surgery/final diagnosis	Dilated loop > 25 mm	83.0% (71.7%-90.4%)	93.0% (55.3%-99.3%)	11.9 (1.2-114.9)/0.2	5/433	NR in retrievable text	IPD design reduces reporting bias; no GRADE	Most conservative estimate; specificity CI so wide the parameter is effectively unestimated
SBO: Meta-analysis with QUADAS-2 (Motavaselian et al[30], 2024)	ED adults with suspected SBO	Mixed	CT/surgery/final diagnosis	Dilated loop > 25 mm	NR here (see source)	0.80 (0.77-0.83)	N/A	21/1977	62% sensitivity; 88% specificity (both P < 0.01)	QUADAS-2: High risk for patient selection and flow/timing in several studies; Egger P = 0.04	Specificity 16 points below the two estimates above; publication bias detected
SBO: Bedside-threshold analysis (Shokoohi et al[11], 2024)	ED adults	EP	CT/surgery	Loop > 2.75 cm (AUC = 0.76, 0.71-0.81); ≤ 1.7 cm 100% sensitivity; > 4 cm	N/A	Approximately 90.7% at > 4 cm	N/A	IPD secondary analysis	N/A	Unvalidated threshold-derivation study	Candidate threshold only; no measurement convention specified; age/sex shift optimum (2.95 cm at ≥ 65 years)
Acute cholecystitis: EP-POCUS meta-analysis (Wilson et al[32], 2024)	ED adults, suspected acute cholecystitis	EP	Final diagnosis	Stones + wall > 3 mm + Murphy sign + pericholecystic fluid	70.9% (62.3%-78.2%)	94.4% (88.2%-97.5%)	12.7/0.31	10 included; estimates from 7/1772	NR in retrievable text	Not reported in retrievable text	Rule-in test; negative scan does not exclude
Acute cholecystitis: All-operator meta-analysis (Huang et al[25], 2023)	Mixed settings, all specialties (EP subgroup)	All operators; EP subgroup	Final diagnosis/pathology	As above	71% (69%-72%); EP 71% (67%-74%)	85% (84%-86%); EP 92% (90%-93%)	N/A	40/8652	89.7% (87%-92%)	QUADAS-2: > 25% of studies high risk (case-control design, non-consecutive enrolment)	Operator specialty changes specificity by 7 points
Acute cholecystitis: Prospective TG18-adjudicated cohort (Nipitkul et al[33], 2026)	ED adults, high disease prevalence	EP	TG18	POCUS criteria vs TG18 (wall > 3 mm vs ≥ 4 mm scales)	86.6% (83.4%-89.4%)	17.1% (12.5-22.5)	NR/NPV 37.0%	1/783	N/A (primary study)	Prospective; single reference standard	Discordant with pooled specificity of 85%-94%; only gallstones were significantly associated with confirmed disease
Gastric: ED intubation cohort (Asokan et al[27], 2023)	ED adults undergoing urgent intubation	EP	Aspiration-relevant gastric content	Antral CSA ≥ 9.27 cm²	100%	87%	N/A	1/100	N/A	Single-centre	Risk stratification against a surrogate endpoint, not diagnosis
Gastric: Fasting IPD meta-analysis (Perlas et al[26], 2024)	Fasting adults (reference range)	Trained sonographers	Endoscopic/measured volume	95th-percentile CSA 9.9 cm² (9.4-10.4); volume 2.3 mL/kg (2.3-2.4)	Grade 0/1 → 98% probability below threshold	N/A	N/A	12/1203	NR in retrievable text	Reference-range derivation	Thresholds do not generalise across position or population
Free fluid: Ectopic pregnancy (Moore et al[31], 2007)	ED women, suspected ectopic pregnancy	EP	Operative intervention	Any free fluid in Morison's pouch	N/A	N/A	LR+ 112 (15-831)	1/242	N/A	Single-centre; estimate rests on 10 fluid-positive patients	Decisive rule-in in a high-pretest obstetric population only
Free fluid: Prehospital FAST meta-analysis (Lin et al[19], 2024)	Prehospital trauma	Prehospital providers	CT/laparotomy	Any free fluid	0.596 (0.345-0.822)	0.970 (0.953-0.983)	N/A	6/1356	94%a	GRADE: Sensitivity very low (inconsistency, imprecision, publication bias); specificity high	Trauma population, indirect evidence for non-traumatic disease; indicates the sensitivity ceiling
Free fluid: Cochrane review, blunt trauma (Stengel et al[18], 2018)	Blunt thoracoabdominal trauma, adults and children	Mixed	CT/laparotomy/clinical follow-up	Any free fluid	0.74 (0.65-0.81); children 0.63 (0.46-0.77)	0.96 (0.94-0.98)	N/A	34 studies	Reported in source	Cochrane methodology	At 28% prevalence, 73 injured adults and 118 injured children missed per 1000 scanned
Appendicitis: POCUS meta-analysis (Matthew Fields et al[35], 2017)	ED adults and children	Non-radiologist physicians; EP subgroup	Pathology/final diagnosis	Non-compressible, dilated appendix	91% (83%-96%); EP subgroup 80%	97% (91%-99%); EP subgroup 92%	N/A	21/NR	99% (99%-100%)	Not reported in retrievable text	Extreme heterogeneity; EP-only performance lower than the headline figure
Appendicitis: Paediatric meta-analysis (Miller et al[36], 2026)	Children	Mixed	Pathology/final diagnosis	Non-compressible, dilated appendix	85.6% (68.9%-94.1%)	90.2%	N/A	8/993	Sensitivity range 53%-100% across studies	Recent; see source	Between-study range wider than the pooled CI implies
Hydronephrosis/renal colic (Wong et al[37], 2018)	ED adults, suspected renal colic	EP	CT	Any hydronephrosis	70.2% (67.1%-73.2%)	N/A	N/A	NR in retrievable text	NR in retrievable text	Not reported in retrievable text	Risk stratification only; cannot exclude
AAA (Shaban et al[34], 2025)	ED adults, symptomatic	EP	CT/operative/final diagnosis	Aortic diameter ≥ 3 cm (aneurysm definition)	98.33%	99.84%	N/A	9/NR	NR in retrievable text	Not reported in retrievable text	Identifies an aneurysmal aorta; does NOT identify rupture, for which CT angiography is the reference standard

^aFor Lin et al[19], 2024 the source reports this 94% number for sensitivity from a χ² test of heterogeneity, not as an I² statistic, and reports 45% for specificity by the same test; the value is reproduced here as published and the column is therefore headed heterogeneity rather than I².

Values are reproduced from the cited sources; no estimates were recalculated. Every value in this table was checked against the cited source; NR denotes a value that the source itself does not report, and is therefore a finding about the source rather than an unverified entry. Full source-by-source extraction details, including the location of each value within its source, are given in Supplementary Table 2. AAA: Abdominal aortic aneurysm; AUC: Area under the receiver-operating-characteristic curve; CI: Confidence interval; CSA: Cross-sectional area; CT: Computed tomography; ED: Emergency department; EP: Emergency physician; GRADE: Grading of Recommendations Assessment, Development and Evaluation; IPD: Individual-patient-data; LR+: Positive likelihood ratio; LR-: Negative likelihood ratio; NPV: Negative predictive value; NR: Not report; QUADAS-2: Quality Assessment of Diagnostic Accuracy Studies 2; SBO: Small-bowel obstruction; TG18: Tokyo Guidelines 2018; POCUS: Point-of-care ultrasound; N/A: Not applicable.

Table 2 Tokyo Guidelines 2018 diagnostic and severity criteria relevant to bedside sonography

Item	Acute cholecystitis	Acute cholangitis
Diagnostic criteria	One local sign of inflammation + one systemic sign = suspected; + characteristic imaging = definite[21]	One item of systemic inflammation + one item of cholestasis or imaging = suspected; all three = definite[88]
Systemic inflammation	N/A	Fever > 38 °C, or laboratory evidence of an inflammatory response[88]
Cholestasis	N/A	Jaundice with total bilirubin ≥ 2 mg/dL, or liver function tests > 1.5 × upper limit of normal[88]
Imaging item	Characteristic imaging findings (wall thickening ≥ 4 mm among them)[21]	Biliary dilatation, or evidence of aetiology (stricture, stone, stent)[88]
Grade I (mild)	No organ dysfunction; mild local inflammatory change[21]	Neither grade II nor grade III criteria met[88]
Grade II (moderate)	Any one of: WBC > 18000/mm³; palpable tender RUQ mass; complaints > 72 hours; marked local inflammation (gangrenous or emphysematous cholecystitis, pericholecystic or hepatic abscess, biliary peritonitis)[21]	Any two of five criteria, one of which is age ≥ 75 years[88]
Grade III (severe)	Dysfunction of any one organ system: Cardiovascular (hypotension requiring dopamine ≥ 5 μg/kg per minute, or any dose of noradrenaline); neurological (decreased consciousness); respiratory (PaO2/FiO2 < 300); renal (oliguria or creatinine > 2.0 mg/dL); hepatic (PT-INR > 1.5); haematological (platelets < 100000/mm³)[21]	Organ dysfunction as for cholecystitis[88]
Management by grade	Grade I and grade II (experienced surgeons): Early laparoscopic cholecystectomy where CCI ≤ 5 and ASA-PS ≤ 2; otherwise, medical treatment and/or gallbladder drainage with interval cholecystectomy. Grade III: Early or urgent biliary drainage with delayed cholecystectomy; upfront surgery only with favourable organ-system failure, no negative predictive factors, CCI ≤ 3, ASA-PS ≤ 2, in an advanced centre[81]	Biliary drainage, urgently in severe disease[88]
Sonographic component of grading	None: Grading uses vital signs, organ-failure laboratory values, WBC, symptom duration and comorbidity indices[21]	None[88]

Criteria are reproduced from Tokyo Guidelines 2018 as cited. No element of severity grading in either condition is sonographic; ultrasound establishes the imaging item of the diagnostic criteria, after which grading is clinical and laboratory-based. ASA-PS: American Society of Anesthesiologists Physical Status; CCI: Charlson Comorbidity Index; PT-INR: Prothrombin time-international normalised ratio; RUQ: Right upper quadrant; WBC: White blood cell count; N/A: Not applicable.

Table 3 The authors’ proposed specification: What a consensus process would need to fix before these applications can be standardised

Consensus item	SBO	Gastric assessment	Free fluid beyond trauma	Biliary tract
Minimum image set	Number of quadrants required for a complete study is undefined; segmental obstruction means an incomplete survey can be falsely negative. Fix: Mandated quadrants and documented images per quadrant	Supine and RLD antral views are used inconsistently; some thresholds are supine-derived and others RLD-derived. Fix: Both positions mandatory, each documented	Number and identity of dependent recesses varies outside the FAST protocol; pelvic views may be omitted in non-trauma scanning. Fix: Defined recess set for the non-traumatic indication	Long-axis and short-axis gallbladder views, wall measurement site and duct view are not standardised. Fix: Mandated views including the point of wall measurement
Measurement convention	No published convention specifies outer-to-outer vs inner-to-inner, plane, or whether maximal or averaged loop diameter is used, a difference capable of exceeding the 2.5 mm separating the 2.5 cm and 2.75 cm thresholds. Fix: Single defined convention	Antral CSA is derived by different formulae and at different antral levels. Fix: One formula, one anatomical level, one patient position per stated threshold	Volume estimation and the distinction between trace, small, moderate and large collections are undefined; agreement falls to kappa 0.48-0.65 for this distinction. Fix: Defined volume categories with anchoring images	Wall thickness is measured at unspecified sites and on discordant scales, > 3 mm in the emergency literature against ≥ 4 mm in TG18. Fix: One threshold, one measurement site, one wall (anterior)
Definition of a positive study	Whether dilatation alone suffices, or dilatation plus abnormal peristalsis, or plus interloop fluid, varies between studies. Fix: Explicit rule for the composite	A positive study means different target volumes in different sources (empty stomach, > 1.25 mL/kg, aspiration-relevant content). Fix: State the target volume with the threshold	Any anechoic fluid vs a clinically significant volume is not distinguished. Fix: Population-specific definition, since physiological pelvic fluid differs by sex and pregnancy status	Number and combination of signs required is unstated; agreement is kappa 0.85 for gallstones but 0.37 for the composite diagnosis. Fix: Defined minimum criteria set, aligned to TG18
Reporting lexicon	Terms for peristaltic patterns and the valvulae sign are used inconsistently across the literature. Fix: Controlled vocabulary with defined terms	Perlas grades 0-2 are well defined but quantitative and qualitative results are reported interchangeably. Fix: Report grade and CSA separately, never as equivalents	Descriptors of volume and location vary. Fix: Standardised recess names and volume categories	Sonographic Murphy sign has no standardised elicitation, defined transducer pressure or accounting for prior analgesia. Fix: Defined elicitation protocol, or removal of the sign from criteria
Reference standard	CT, surgical findings and final clinical diagnosis are used interchangeably across pooled studies. Fix: Single specified standard, or pre-specified stratification by standard	Aspirated volume, endoscopic volume and model-predicted volume are used as equivalents. Fix: One standard; and outcome studies linking measurement to aspiration rather than to volume	Trauma-derived standards (CT, laparotomy) are applied to non-traumatic populations. Fix: Indication-specific reference standard	Final diagnosis, pathology and TG18 give materially different specificity (17.1% vs 85%-94%). Fix: TG18 as the uniform standard, with the index test measured on the same scale
Training volume for credentialing	No application-specific minimum; the attending-resident sensitivity gap is 14.7 percentage points. Fix: Application-specific case minimum with competency assessment	No emergency-setting training standard exists; the available reliability study used three raters and healthy volunteers. Fix: Defined supervised case volume	FAST credentialing exists but is trauma-specific and does not cover non-traumatic indications. Fix: Extension of credentialing to the non-traumatic indication	Credentialing exists in most curricula but is not tied to demonstrated agreement on wall thickness or the Murphy sign. Fix: Competency demonstrated per sign, not per application
Quality assurance	No archived-image review requirement; loop measurement cannot be audited if images are not stored. Fix: Mandatory archiving of the measured loop	No QA mechanism described in any cited source. Fix: Archived antral images with periodic measurement audit	Where archiving exists it is trauma-oriented. Fix: QA review of non-traumatic studies, with attention to small collections	QA review is described in stewardship literature but is not sign-specific. Fix: Periodic audit of wall measurement and of Murphy-sign documentation
Priority reliability studies required	Inter-observer agreement for loop-diameter measurement: No published kappa or ICC was identified for this measurement, on which the entire branch turns	Inter-observer agreement for antral CSA in an emergency population; and any study linking measurement to aspiration rather than to volume	Inter-observer agreement for detecting a small collection in a non-traumatic emergency population, none identified	Inter-observer agreement for millimetre wall-thickness measurement in an emergency setting (none identified) and a second, multicentre study of the sonographic Murphy sign

Each cell states the current position in the literature followed by the specific item a consensus process would need to fix. Statements that no data were identified refer to the searches described in the METHODOLOGY section. CSA: Cross-sectional area; CT: Computed tomography; FAST: Focused Assessment with Sonography for Trauma; ICC: Intraclass correlation coefficient; QA: Quality assurance; RLD: Right lateral decubitus; TG18: Tokyo Guidelines 2018; SBO: Small-bowel obstruction.

Table 4 Evidence-versus-proposal matrix for each action node of the integrated algorithm (Figure 1): What the node rests on, and whether it is derived from evidence or proposed by the authors

Algorithm action node	Evidence type	Evidence supporting the node	Status	Ref.
Step 1: Instability/red-flag check precedes any scan	Expert recommendation	Consensus statements on emergency POCUS scope; no comparative trial of scan-first vs resuscitate-first	Authors’ proposal	Kameda and Taniguchi[7], Oto et al[8]
Step 2: Operator competency precondition	Evidence-informed	Operator-level subgroup estimates differ by application and do not all run the same way: For appendicitis the EP subgroup is lower than the pooled estimate on both axes (sensitivity 80% vs 91%, specificity 92% vs 97%), whereas for cholecystitis the EP subgroup matches the pooled sensitivity (71% vs 71%) and exceeds the pooled specificity (92% vs 85%). Competency is therefore required as a precondition because performance is operator-dependent in an application-specific direction, not because EP performance is uniformly lower	Evidence-based (subgroup estimates), authors’ proposal (credentialling requirement)	Huang et al[25], Matthew Fields et al[35]
Step 3: Symptom cluster sets pretest probability and orders the scans	Authors’ construction	No study compares symptom-ordered POCUS sequencing against a fixed protocol	Authors’ proposal	N/A
Biliary branch: Gallstones + sonographic Murphy sign + wall > 3 mm as the rule-in trigger	Evidence-based	Pooled specificity 94.4% (88.2%-97.5%) for EP-performed POCUS; TG18 uses wall ≥ 4 mm	Evidence-based	Yokoe et al[21], Wilson et al[32]
Biliary branch: Negative scan does not exclude cholecystitis	Evidence-based	Pooled EP sensitivity 70.9% (62.3%-78.2%); LR- accordingly poor	Evidence-based	Wilson et al[32]
Biliary branch; fever + jaundice + dilated duct triggers the cholangitis pathway	Guideline-based	TG18 diagnostic criteria (systemic inflammation + cholestasis + imaging) and severity grading	Evidence-based (guideline)	Okamoto et al[81], Kiriyama et al[88]
SBO branch: Dilated loops > 2.5 cm as the rule-in trigger	Evidence-based	Pooled sensitivity 92.4% (89.0%-94.7%), specificity 96.6% (88.4%-99.1%), LR+ 27.5	Evidence-based	Gottlieb et al[9]
SBO branch: 2.75 cm as a candidate refined threshold	Authors’ construction	Proposed in a bedside-threshold analysis; no reliability data exist for bowel-loop diameter at this precision	Authors’ proposal: Explicitly unvalidated	Shokoohi et al[11]
SBO branch, CT still required for transition point, aetiology, ischaemia, perforation	Evidence-based	Consistent statement across the SBO syntheses; POCUS not evaluated for these endpoints	Evidence-based	Gottlieb et al[9], Shokoohi et al[10], Motavaselian et al[30]
Free-fluid branch, free fluid in Morison’s pouch or pelvis as the rule-in trigger	Evidence-based	Ectopic pregnancy cohort; prehospital FAST pooled specificity 0.970 (0.953-0.983)	Evidence-based	Lin et al[19], Moore et al[31]
Free-fluid branch: Ectopic pregnancy excluded only by seeing an intrauterine pregnancy	Evidence-based	Pooled FAST sensitivity 0.74 (0.65-0.81) in blunt trauma; absent free fluid carries no exclusionary value for ectopic pregnancy	Evidence-based	Stengel et al[18], Moore et al[31]
Aorta/renal branch, aortic diameter ≥ 3 cm; POCUS does not identify rupture	Evidence-based	Aneurysm detection sensitivity 98.3%, specificity 99.8%; no pooled estimate for rupture detection	Evidence-based	Shaban et al[34]
Gastric parallel branch: Perlas grade and antral CSA stratify aspiration risk	Evidence-based	IPD meta-analysis: Grade 0/1 gives 98% probability of being below the risk threshold; ED intubation cohort sensitivity 100%, specificity 87%	Evidence-based (against a surrogate endpoint)	Perlas et al[26], Asokan et al[27]
Gastric parallel branch; thresholds are position- and population-specific, not interchangeable	Evidence-based	Distinct CSA thresholds by position and population across the source studies	Evidence-based	Perlas et al[26]
Third exit; non-diagnostic study treated separately from a negative study	Authors’ construction	No source study reports a distinct action pathway for non-diagnostic examinations	Authors’ proposal, a principal original contribution	N/A
Serial scanning after an interval where the picture is evolving	Expert recommendation	No comparative evidence for serial abdominal POCUS in this setting	Authors’ proposal	N/A
Secondary redirect applications when the entry scan is negative or non-diagnostic	Evidence-based (component estimates), authors’ construction (the redirect rule)	Appendicitis EP sensitivity 80%, specificity 92%; hydronephrosis sensitivity 70.2%; AAA detection 98.3%	Mixed, estimates evidence-based, sequencing proposed	Shaban et al[34], Matthew Fields et al[35], Miller et al[36], Wong et al[37]
Governing principle, every application rules in better than it rules out	Evidence-based	Direct consequence of the sensitivity/specificity asymmetry documented in Table 1	Evidence-based	Gottlieb et al[9], Shokoohi et al[10], Stengel et al[18], Lin et al[19], Huang et al[25], Wilson et al[32]

N/A in the reference column indicates that no source study addresses the node, which is therefore an authors’ proposal rather than an evidence-derived step. It is provided so that a reader can separate the evidence synthesised in this review from the pathway the authors construct from it; the algorithm as a whole has not been prospectively validated. AAA: Abdominal aortic aneurysm; CSA: Cross-sectional area; CT: Computed tomography; ED: Emergency department; EP: Emergency physician; IPD: Individual-patient-data; LR+: Positive likelihood ratio; LR-: Negative likelihood ratio; SBO: Small-bowel obstruction; TG18: Tokyo Guidelines 2018; POCUS: Point-of-care ultrasound; N/A: Not applicable; FAST: Focused Assessment with Sonography for Trauma.